Torque control means for power operated tools



1?2 1968 R. F. STATES 3,361,218

TORQUE CONTROL MEANS FOR POWER OPERATED TOOLS Filed July 14, 1965 2 SheetS-Sheet 1 Jan. 2, 1968 I' R' F- STATES 3,361,218

TORQUE CONTROL MEANs'FoR POWER OPERATED TooLs A Filed July 14, 1965 Sheets-Sheet 2 za f Z661 if United States Patent O 3,361,218 TURQUE CGNTRGL MEANS FR POWER OPERATED TOOLS Ronald Frederick States, Hendon, London, England, assignor to Desoutter Brothers Limited, London, England, a British company Filed July 14, 1965, Ser. No. 471,817 Claims priority, application Great Britain, Aug. 20, 1964, 34,040/64 6 Claims. (Cl. 173-12) ABSTRACT F THE DISCLOSURE A hand-held power tool particularly a pneumatically powered Spanner or wrench in which lthe tool is driven by a worm and worm-wheel assemblage and the maximum torque delivered being c-ontrolled by the longitudinal movement of the worm due to the action of the torque developed by the tool.

The invention relates t-o torque control means for power operated tools and more particularly but not exclusively to pneumatically powered hand held spanners or wrenches, while the object of the invention is to provide a hand held power operated .tool in which the maximum torque applied by the tool is automatically controlled.

The invention is directed to a hand-held power operated tool in which the head of the tool is driven by a motor by way of a worm and worm-wheel characterized in that the worm is mounted in bearings for longitudinal movement against the action of a spring under the reaction to the torque applied by the tool, with the longitudinal movement being used to interrupt the drive when the torque reaches a predetermined value.

The invention relates to a hand-held power operated tool as set forth in the preceding paragraph in which the motor is pneumatically operated and the air supply to the motor is interrupted when the torque reaches a predetermined value.

The invention still further relates to a hand held power operated tool as set forth in the preceding paragraph in which the a-ir from the supply passes to the motor by way of a pop-pet valve which is urged in a direction to open against the pressure of air passing to the motor by air pressure controlled by a transfer valve which is operated to interrupt the latter air pressure when the torque reaches the predetermined value to close the poppet valve.

The accompanying drawing shows, by way of example only, one embodiment of the invention in which FIGURE l is a longitudinal section of the tool.

FIGURE 2 is a View taken along the line 2 2 of FIG- URE 1 the view looking in the direction of the arrows and being on an enlarged scale and FIGURE 3 is a view taken along the line 3-3 of FIGURE 2 the view looking in the direction of the arrows The tool illustrated comprises a body portion 1 and a handle portion 2 rigidly connected to the body portion. The body portion includes a cylindrical casing 3 which houses a vane type pneumatic motor 4 and an epicyclic reduction gear 5 which is driven by a shaft 6 and which in turn drives an output shaft 7 having thereon a worm 8 which engages with a worm wheel 9. At the center of the worm wheel 9 is provided the hexagonal aperture 10 for engagement with the hexagonal head of a bol-t or nut being tightened by the tool.

The drive between the epicyclic gear 5 and the shaft 7 is by way of splines 7a on members 7b and 7c so that the shaft 7 can move longitudinally in respect of the member 7b against a action of helical spring 7d upon the flanges 7e and 7f.

The outer end of the shaft 7 rests upon a ball 8a when the tool is at rest, but under the reaction to the torque applied to the bolt or nut the shaft 7 moves away from ball 8a a small distance and is supported axially in a needle roller bearing 8b.

The handle portion 2 is provided with a connector 15 to which the tool air line is connected. The supply of air to the tool is controlled -by a ball valve 16 operated by a trigger 17 by way of a rod 18 against the action of a spring 19.

The air passes down the handle portion 2 by way of bore 20 to a cavity 21, through an open poppet valve 30 into passages 36a and 36h one on each side of and parallel with a poppet valve 30 (see FIG. 2) into a cavity 39 at the rear end of the motor 4.

At the same time the air from cavity 21 enters a bore Z2 by way of a lter 22a, and passing along cross-bore 23a and through ports 26a and 26b in a sleeve 26C, in which a transfer valve 25 works, and by way of the cross- -bore 27a enters cylindrical space 29 at the end of the poppet valve 30. The combined effect of a spring 35 and the pressure of the air in the cavity below the poppet valve 30 overcome the pressure of the air in the cavity 21 on the head of the valve, and the valve therefore remains open.

When the torque exerted upon the nut or bolt is such that the shaft 7 moves longitudinally, it moves rod 7g and thus the transfer valve 2=5 against the action of spring 24, and continues to move until the port 26a is closed, with the result that the passage of air to the space 29 below the poppet valve 30 is interrupted, and at the same time as port 26a is closed, the `space 29 is vented by way of the annular space 26d in the sleeve 26e and port 26e to annular groove 26]'` and by way of radial bores (not shown) enters groove 26g from whence it is exhausted to atmosphere as bore 26h.

The poppet valve then closes due to the pressure of air in the cavity 21, overcoming the reistance of the spring 35, and the motor stops, even though the trigger valve in ythe handle is still open.

The ports 26a, 26b' and 26e are formed in the sleeve 26C, which is movable longitudinally by a cam 42a, which engages upon anged plug 42b in the sleeve against the action of dished springs 42C. The position of the sleeve may therefore be set so that the port 26a is closed at one of a number of different values of ltorque as required.

The cam 42a is formed upon a hexagonal shaft 42d and is provided with a knob 42e by which the position of the cam is set to the required value of torque. Click stops are provided for the knob 42e to retain it in each of a number of alternative positions by means of a spring loaded ball engaging in recesses in the knob.

In operation, it is merely necessary to engage the hexagonal aperture 10 upon the nut or bolt it is required to tighten, place the hand around the handle portion and press the trigger. As soon as the required torque has been reached the motor stops. The trigger is then released and the tool removed.

Seeing that the worm 8 and the worm wheel 9 are designed to be driven in both directions, and the motor offers no resistance when the supply of air is interrupted, the head of the nut or bolt is relieved of pressure when the motor stops and therefore no higher torque can be applied by bearing upon the handle.

The value of torque at which the tool becomes free upon the nut or bolt head is governed by setting of the value by the knob 42e and not by the power developed by the motor. Consequently, if the pressure of air supply to the tool should fall and the motor stall at a lower value of torque, the tool cannot be removed until the motor is freed by cutting off the supply of air by releasing the trigger 17. However, the full torque required can still a be applied to the bolt by manual leverage upon the handle while the motor is held stationary by the reduced air pressure. When full torque has been applied the transfer valve automatically cuts off the air and frees the motor, and the tool rotates freely round the bolt.

Although the invention is hereinbefore described with reference to a Spanner or wrench, it is to be understood that the invention is also adaptable to tools of other types and used for other purposes, while details for carrying the invention into effect may be varied without departing from the scope of the invention claimed.

I Claim:

1. A hand-held power operated tool comprising a casing having opposite ends, a handle at one end of the casing, a nut-engaging means at the opposite end of the casing, a motor mounted within the casing, a worm drivingly connected to the motor, a worm-wheel in operative engagement with the worm operably coupled with the nut-engaging means, an abutment member within the casing, spring means mounted against said abutment member, bearing means in which the worm is mounted for longitudinal movement against the action of said spring means under the reaction to the torque applied by the tool, and motor power control means operably connected to said worm for interrupting the drive when the torque reaches a predetermined value.

2. The hand-held power operated tool as claimed in claim 1 in which the motor is pneumatically operated and is provided with air supply means, said motor power control means including a poppet valve in the air supply means, a transfer valve, said poppet valve being urged in the opening direction against the pressure of air passing through the motor by pressure air controlled by the transfer valve, and means operrably connecting the transfer valve to the worm for closing when the torque reaches said predetermined value thereby allowing the poppet valve to close.

3. The hand-held power operated tool as claimed in claim 2 in which said transfer valve is dened by a shuttle valve, a ported sleeve in which said valve operates and said sleeve being adjustable longitudinally for varying the value of the torque at which the pressure air to the poppet valve is interrupted.

4. The hand-held power operated tool as claimed in claim 3 in which said poppet valve is provided with a stem, a cylindrical cavity below the poppet valve in which said stem functions as a piston and to which pressure air from the transfer valve is admitted to hold the valve open while the tool is operating, and a helical spring in the cavity for assisting the pressure air to hold the valve open.

5. The hand-held power operated tool as claimed in claim 3 including a rotatable cam and a spring for urging the ported sleeve against the cam with the longitudinal position of the sleeve being adjusted by the rotation of the cam.

6. The handheld power operated tool as claimed in claim 2 in which the connection between the transfer valve and the worm includes a rod passing through a bore extending through the motor.

References Cited UNITED STATES PATENTS 1,346,716 7/1920 Lee 8l-57.44 1,437,017 11/1922 Roberts 81-51.4 1,479,178 1/1924 Harvey 81-52.4 2,342,783 2/1944 Aron et al. 173-93 3,162,250 12/1964 Sindelar 173-12 3,174,606 3/1965 Hornschuch et al. 173-12 FRED C. MATTERN, I R., Primary Examinez'.

L. P. KESSLER, Assistant Examiner. 

